Fluid couplings have been known for some time. They are advantageously used in particular for connecting a user to an electric motor or to a heat engine such as a diesel engine of the type used in the marine field.
It is known to construct fluid couplings provided with a delay chamber which, when the engine is not operating, contains a large part of the fluid for transmitting motion between the driving rotor and the driven rotor. Following the starting of the engine, this fluid passes, at a set rate, from the delay chamber to the working chamber containing the rotors, to allow progressive transfer of the drive torque from the driving rotor to the driven rotor, ie from the engine to the user. By suitably setting the rate of fluid passage from the delay chamber to the rotor chamber, the connection lag between the engine and the user can be regulated.
However, this known coupling-delay chamber arrangement does not enable an effective lag in said connection to be achieved because of obvious dimensional limitations on the coupling. In this respect, because of the manner in which such a coupling is structured, the delay chamber has only a small volume in order to avoid problems in transferring the fluid from the delay chamber to the working chamber, and in any event it is desirable to limit the overall size of the coupling. Consequently the amount of fluid which can be contained in such a chamber is likewise limited, meaning that the lag period obtainable with such a coupling is also limited.
Other couplings allowing a longer lag in connecting the engine to the user are also known. Such couplings are however of complicated construction in that they use a reservoir external to the coupling to contain the fluid to be fed to the coupling, plus external circulation pumps.